Apparatus for pressure homogenization



Sept. 16, 1958 L. H. REES 2,852,237

APPARATUS FOR PRESSURE HOMOGENIZATION Filed Jan. 9. 1956 2 Sheets-Sheet 1 INVENTOR. LANCELOT H.v Rz-zas H/s A T TORNEYS Sept. 16, 1958 L. H. REES 2,852,237

APPARATUS FOR PRESSURE HOMOGENIZATION Filed Jan. 9. 1956 2 Shets-Sheet 2 fiiiiiisl l a" INVENTOR.

5 LANCfiLOT H. Peas By M J ejvg Ms A T TORNE vs United States Patent 2,852,237 APPARATUS FoR PRESSURE HOMOGENIZATION Lancelot H. Rees, Westwood, Mass., assignor to Manton- Gaulin Manufacturing Company, Inc., Everett, Mass., a corporation of Massachusetts Application January 9, 1956, Serial No. 558,083 7 Claims. (Cl. 259-4) This invention relates to pressure homogenization of fluid materials and to equipment therefor. More particularly it concerns homogenization of fluid materials by forcing them under positive pressures of a high order through a restricted zone, imparting very high velocities to the material in so doing. Such restricted zone is provided by adjacent surfaces resiliently urged against the fluid pressure by controllable biasing means into abutting relation, and the material is forced between these surfaces whereby it is subjected to drastic shearing action. Commonly also the fluid is caused to strike a surface disposed transversely of the flow as it emerges from between the first set of surfaces, and the change in direction of the material on striking the transverse surface further assists in breakdown of the particle size of the material to enhance the uniformity and stability of suspension.

Pressure homogenization as thus defined is generally accomplished by a homogenizer valve providing the aforesaid resiliently abutting and transversely disposed surfaces in conjunction with a high pressure pump for supplying the fluid under pressure to the valve, and it is an object of the present invention to provide improvements in valve constructions adapted for this purpose. Certain portions of these valves, notably the valve seats and valve plugs or closing members, become rapidly worn, especially when the material being processed is abrasive in nature, as many "are, particularly at the pressures involved. The expense 'of replacing these various valve components therefore therefore, is to provide a homogenizer valve construction in which those portions of the valve assembly which are most subject to wear are made as removable and replaceable inserts which can be readily removed and replaced when they have become worn, without replacing large and expensive parts of the valve assembly.

The use of replaceable inserts at points of wear in mechanical equipment is, of course, generally known. In the field of pressure homogenization, however, there are special problems arising from several sources which by ordinary standards have rendered this expedient impractical in designs heretofore proposed. For example, since one of the principal uses of pressure homogenizers isin vprocessing food products, the degree of cleanliness, if not complete sterility, required makes it imperative that cracks, threads and similar depressions or crevices be avoided so that there will be a minimum of opportunity for food particles to become lodged in the equipment in places which make it difficult to clean and to maintain in such condition. Similar considerations obtain in the 'ing head of the valve plug,

processing of other materials, such as paint pigments,

for example, where it is imperative that complete cleaning of the homogenizer components be readily possible after use so as-to avoid contamination of subsequent pigment of a different color processed in the unit. Under the extreme pressures Which are employed in pressure homogenization, and generally these run from a minimum of around 1000 pounds per square inch to 10,000 pounds per square inch, or even more, the abrasiveness of the materials being processed becomes of vital significance. Naturally, the use of extremely hard abrasion resistant materials for fabrication of the homogenizer parts suggests itself, but such materials almost invariably are extremely brittle and of low tensile strength so that they present serious problems of design and fabrication in order to meet the high stress load which is placed upon them by reason of the highoperating pressures. Prior attempts to provide a homogenizer valve construction employing hard abrasion resistant inserts have been faced with satisfying the conflicting requirements of valve components having excellent tensile strength yet extreme abrasion resistance, simple design of minimum size and ease of machinability, freedom from cracks or crevices where accumulation of processed materials might occur,

and ready access of the valve components for thorough cleaning and replacement when excessively worn. The more common highly abrasion resistant materials, such as specially hardened steels or chrome or tungsten carbides, have generally failed in previous attempts, owing to lack of mechanical strength. Cracking and disintegration of the abrasion resistant parts often resulted, therefore, long prior to any appreciable deterioration occasioned by abrasive wear.

'It is a further object of the present invention, therefore, to provide in pressure homogenizing valves at the points of maximum wear removable and replaceable inserts of hard, abrasion resistant material which will withstand the severe loads imposed by the homogenizing pressures applied without cracking. At the same time there is provided a valve design which permits the ready assembly of the internal valve components without the use of tools and thereby avoids the liability of marring the parts and rendering them unfit for use.

Maximum wear occurs at the valve seat and cooperatand at the point of discharge of fluid from between these cooperating surfaces. Accordingly the present invention provides an insert in the form of a valve seat member which is held in place without reliance upon threads or other special securing means, which are objectionable for many reasons, the insert being so designed and positioned that the fluid pressure itself presses the insert firmly into place in sealingengagement with its support. A removable insert is also provided in the cooperating valve plug or valve closing member. This is so constructed as to avoid problems of concentricity with respect to the valve seat, being designed toposition itself and be held in proper location during operation of the valve by the fluid pressure also.

A still further feature of the invention is the provision of 'a'homogenizing valve in which the valve seat or in- -sert is ofannular configuration and is provided within 'its central aperture with a significantly reduced orifice closed,.a surprisingly great improvement is obtained in homogenization of compositions containing particles of very small ultimate size.

In general, therefore, the invention provides a pressure homogenizer valve construction primarily of interest for abrasive products where rapid wear of the component parts of the valve may take place. The valve construction afiords easy replacement of worn components and this facilitates choice of materials for the replaceable valve components, making it economically practical for the processer to have replaceable components of various materials on hand for use by him, depending upon the nature of the fluid material being treated.

These and other objects and features of the invention will become apparent from the following description of several embodiments of the invention illustrated in the accompanying drawings in which:

Fig. 1 is a plan view from above a complete pressure homogenizer;

Fig. 2 is a view in side elevation, partly in section, on line 22 of Fig. 1, showing the pump cylinder and homogenizer valve secured thereto;

Fig. 3 is a detailed view in plan, partly in section, taken on line 33 of Fig. 2', and

Figs. 4 and 5 are fragmentary views in section of the valve assembly, showing modifications of the construction in Fig. 3.

Referring to Fig. l, the pressure homogenizer comprises a housing 22 enclosing an electric motor or other suitable source of driving power, not shown. The motor drives a crank shaft (also not shown) to reciprocate plungers 24 which Work into a pump cylinder block 26. In this instance there are three plungers providing a triplex action pump. As seen more particularly in Fig. 2, suitable intake and outlet check valves 28 and 30, respectively, are located in the cylinder block 26 in conjunction with each plunger. Fluid is supplied to an intake passage 32 bored in the lower side of the block and is sucked up through the respective intake valve 28 on the intake stroke of each plunger 24, successively, and then expelled through the respective outlet valve 30 into the high pressure discharge chamber 34 in the top of cylinder block 26. An outlet passage 36 in the block leads from the high pressure discharge chamber 34 to the inlet port of a homogenizer valve assembly 38 bolted to the side of the cylinder block.

As shown more particularly in Fig. 3, valve assembly 38 includes a main body 40, a hand wheel support 42, and an operating hand wheel 44. Valve body 40 is provided with a through-bore 46, and is counter-bored at the end adjacent the cylinder block 26 to form a series of inwardly stepped recesses 48, and 52 concentric on bore 46 and the outlet passage 36 of the cylinder block. A valve plug or valve closing member 54 is disposed in through-bore 46 in snug, sliding engagement therewith and carries in appropriate circumferential grooves 55 a pair of O-rings 56 for effecting a fluid tight seal with the walls of the bore. Plug 54 has a pilot hole 58 at its upstream end, and carries a removable tip 60 having a stud 62 which makes an easy fit in the pilot hole 58. The plug tip presents a smooth flat surface 64 of substantial cross sectional area transversely of the axis of the through-bore 46.

Within the recess 48 in valve body 40 as illustrated in Fig. 3, there is positioned a removable composite valve seat comprising an annular holder member 66 of any suitable steel, and a separate annular valve seat portion 68 of hard abrasion resistant material such as a metal carbide. Holder 66 fits snugly at its external periphery within the wall of recess 48, and bottoms on shoulder 70 lying between recesses 48 and 50 so that its inner face is recessed slightly below the inner face of the body 40. At its interior wall 67, holder 66 tapers inwardly in the direction of fluid flow, and the external surface 69 of seat insert 68 is similarly tapered so that when inserted into the holder, a fluid tight seal is effected between the two members. Seat insert 68 is frusto-conical in shape and is somewhat longer, axially, than the axial extent of holder 66 so as to project to a point substantially midway along the axial extent of recess 50. The annular end wall 72 of insert 68 is thus disposed in abutting relation to the surface 64 of plug tip 60, the two members coextending radially to provide mating surfaces of substantial area. Surrounding the valve seat insert 68 and plug tip 60 adjacent their abutting faces there is disposed an annular breaker ring 74 which seats in the pocket or recess 50 and bottoms on shoulder 76 disposed between recesses 50 and 52. The inner diameter of the breaker ring 74 is slightly greater than that of the external diameter of the valve insert and the plug tip at this point so that there is a small peripheral space 75 between that surface and the seat insert and plug providing a passage for the outflow of fluid material. A similar peripheral space 77 is formed between the plug 54 and the wall of recess 52, and connects with space 75. A lateral passage 78 in valve body 40 intersects the throughbore 46 within recess 52 to provide communication between space 77 and a discharge port 80 of the valve.

Hand wheel support 42 has a flanged base portion 82 through which holddown bolts 84 pass, as seen best in Fig. 2. These bolts also pass through holes bored through valve body 40, and threadedly engage tapped holes 86 in the cylinder block 26 to secure the valve assembly to the cylinder block in fluid tight relation. A gasket 88 is positioned between the recessed valve seat holder 66 and the exposed face of the cylinder block 26 to form a pressure seal at this point. Gasket 88 is backed up by the body 40 of the valve which prevents it from being blown out by the high pressures to which it is subjected during operation of the unit.

Control of the pressure which is built up by the pump in order to force fluid from the discharge passage 36 in ,cylinder block 26 through the valve is determined primarily by the pressure applied to the rear of plug 54. To permit adjustment of this pressure, hand wheel 44 is provided with an internally threaded central hub 90 which engages external threads on the support 42. The hand wheel carries a valve rod 92 which passes freely through a bore 96 in the hub 90 and a cap nut 94 is secured to the outer end of the rod. The latter has a skirt or flange 98 spaced somewhat from its inner end, and a helical compression spring 100 is disposed around the rod and confined between the skirt and the underside of hub 90. A hearing washer 102 is positioned between the hub and the spring to prevent wear on the hub itself, and a second bearing washer 103 is likewise positioned between the outer end of the hub and cap nut 94. When the hand wheel assembly, including the valve rod, is screwed onto the threaded shank of support 42, the nose of the valve rod passes freely through an aperture 104 in the base of the support and comes in contact with the rear face of plug 54, pushing the. tip 60 into abutment with surface 72 of insert 68. As the hand wheel is turned farther in a tightening direction, spring 100 is compressed by the sliding of hub 90 down on rod 92, and the surfaces 64 and 72 are resiliently compressed together. As the fluid pressure in passage 36 is built up by the pump, it reaches a point at which it is sufficient to displace plug 54 against the urging of spring 100, whereupon fluid may pass between surfaces 72 and 64, out through the small peripheral passageways v 75 and 77 to outlet passage 78 and port 80.

The structural simplicity of the foregoing valve arrangement, affording minimum likelihood of accumulation of particles of material being processed owing to the absence of any cracks or crevices is apparent from the illustration in the drawings. Moreover, with respect to valve insert 68 and plug tip 60, easy replacement of these parts, which are the points most subject to wear, is ob tained, as the only holding means for retaining these parts in position is the pressure of the fluid being treated forcing these parts continuously into seating engagement with their associated supporting members. It will be apparent also that the size of these parts can be kept very small so as to minimize the amount of expensive material from which these parts are fabricated. The simple design of the parts here shown is such that they can be readily fabri cated, even from the hardest materials such as the metal carbides mentioned previously, since about the only machining operations necessary in forming them are grinding operations. As has been mentioned hereinbefore, because of the heavy stress applied to the components by the high fluid pressure, valve insert 68 is made separable from its holder 66, and by so doing the liability of fracture of the valve seat members is substantially eliminated.

A modification of the foregoing valve construction is shown in Fig. 4, in which a valve insert 68 is provided with an internal constriction forming an orifice 106 of greatly reduced cross sectional area. As will be seen from the drawings, this constriction is disposed intermediate the axial extent of the valve seat insert, and the inner wall of the insert flares outwardly at 108 from constriction 106 to substantially the same diameter as at the upstream or entrance end of the passageway through the insert. This outward flaring forms a small. expansion chamber 110 immediately preceding the point at which fluid passes between the surfaces 72' and 64. It has been found that providing a severe constriction such as orifice 106 in the valve seat insert, followed by an expansion chamber immediately preceding the shearing action afforded by passage of the fluid material between the closely spaced surfaces, results in tremendously improved product, particularly when handling materials having a small ultimate particle size in the range below one-half micron. The results obtained appear to be especially good where the size of the orifice 106 is so proportioned as to cause the fluid passing through it to have a velocity upon entering the expansion space 110 on the order of at least 100 feet per second.

In Fig. 5 a further modification of the valve seat insert is illustrated. In this instance an insert 68" has a double conical taper providing inwardly and outwardly flared walls 112, 114. These flared walls intersect to provide a point of maximum constriction 116 intermediate the axial extent of the insert 68". A separable orifice plug 118, having an external surface shaped to snugly fit within the inwardly tapered surface 112 of the insert is positioned in the latter. Orifice plug 118 is pierced to provide a passage 120 therethrough. Thus in this arrangement the valve seat assembly is composed of a replaceable plug 118 nested within a valve insert 68", which latter in turn nests within the holder 66. In this manner, variations in the size of the passage 120 can be readily obtained very economically by simply replacing insert plug 118 with similar plugs having internal bores of varying diameters.

In the operation of the homogenizer valve, it is customary to start pumping the fluid through the valve with the latter positioned in open condition, that is, with control handle 44 unscrewed to permit plug 54 to be easily pushed back by oncoming fluid so as to oflfer little or no resistance to the passage of fluid through the valve. Once flow of the fluid has been established the control handle 44 is then turned to compress helical spring 100 which in turn presses against the plug 54 as described above to cause the fluid pressure to be built up to the desired amount for the particular material concerned. The resilience of spring 100 thereafter permits rapid vibrations or axial shifting of the plug 54 and tip 60 to maintain the pressure essentially constant as the material passes through the valve. In so doing it is subjected to severe shearing action by surfaces 64 and 72, which causes breakdown of the particles suspended in the fluid material. Upon emerging from between the aforesaid surfaces at a high rate of velocity, the fluid is also caused to strike the breaker ring 74 in a substantially perpendicular direction, and this impact and sudden change inflow direction causes further breakdown of the particles, thereby efiecting more uniform particle size and better suspension. The fluid then passes out through the outlet passage 78 to port 80 as previously mentioned.

The operation of a homogenizer employing valves such as that shown in Figs. 4 and 5 of the accompanying drawings is essentially the same. However, in this instance, the preliminary constriction or orifice 106. or 120, as the casemaybe, effects a resistance to the through-flow of fluid, causing substantial back pressure to be built up in the high pressure chamber 34 of the cylinder block 26 even with no spring pressure or plug 54. It has been found in practice that in this case it is desirable to provide a restricted orifice so sized that a back pressure of between 3000 and 7000 pounds per square inch is indicated on homogenizing pressure gauge 122 (Figs. 1 and 2) before the valve 38 is closed at all. After the flow of fluid through the valve has then been established, the valve is closed as before to bring the total pressure to some value higher than the initial, valve-open condition. By operating in this manner a surprising improvement in uniformity of dispersion is obtained when handling materials of small ultimate particle size as mentioned hereinabove. No such improvement is obtained where the same type of valve and valve seat, but without the restricting orifice in the latter, is used at corresponding homogenization pressures. In practice it has been found that orifices on the order of 0.020 to 0.030 inch, for example, are especially desirable for obtaining particularly uniform dispersion of particles in a slurry. Such small orifices, however, are of course easily plugged if the slurry contains agglomerates of anysubstantial size, and consequently careful screening or filtering of the slurry prior to running it through the homogenizer is necessary. As a practicalmatter, orifices on the order of A to /s of an inch are found to provide excellent results and to be free of the difficulty arising from the occasional inclusion of agglomerates just mentioned.

Various modifications in the design of the valves illustrated and described herein will be apparent, and all such modifications as come within the scope of the appended claims are accordingly intended to be included therein.

I claim:

1. In a valve for a pressure homogenizer, a valve body having a through-bore stepped progressively inward from the inlet end of the valve and a discharge passage communicating laterally with said bore, valve means in said bore for restricting the flow of fluid there through and-resilient control means for positioning said valve means, said valve means including a removable annular valve seat insert disposed in the upstream step of said bore, said insert being frusto-conical with its outer wall tapering inwardly in the direction of fluid flow, and an axially slidable plug disposed in fluid sealing engagement with the wall of a downstream step in the bore of said body, a removable tip carried loosely in the upstream end of said plug and having a surface disposed to abut against and conform with the opposing downstream end face of said annular seat insert, forming with the latter radially coextending surfaces of substantial area between which fluid material entering said valve must pass, said plug being engaged at its downstream end by said control means for resiliently urging said tip into abutting relation with the end face of said annular valve seat insert.

2. A pressure homogenizer valve as defined in claim 1, wherein said removable annular seat insert is provided in its inner wall with a constriction located axially intermediate the ends of the aperture in said seat, said aperture being radially enlarged at the downstream side of said constriction to provide a small expansion chamber immediately adjacent the abutting face of said removable plug tip.

3. A pressure homogenizing valve as defined in claim 1,

which further includes a removable annular breaker ring disposed in a downstream step in said bore in said valve body and in which it is confined by said annular valve seat, said breaker ring surrounding said valve seat insert and plug tip adjacent the abutting faces thereof, the size of the aperture in said breaker ring being suflicientl y large to provide peripheral spacing between it and said seat insert and plug tip.

4. A pressure homogenizer valve as defined in claim 3, wherein said valve seat insert, plug tip and breaker ring are formed of extremely hard, abrasion resistant material.

5. A pressure homogenizer valve as defined in claim 4, wherein said abrasion resistant material is a metal carbide.

6. A pressure homogenizer valve as defined in claim 1, wherein said annular valve seat insert has an internal constriction in the aperture thereof located intermediate the axialextent of the aperture, said aperture flaring outwardly from said restriction toward each end of said seat insert.

7. A pressure homogenizer valve as defined in claim 6, which further includes a removable orifice plug seated in fluid tight relation in the tapered aperture of said valve seat insert at the upstream side of said constriction.

References Cited in the file of this patent UNITED STATES PATENTS 1,973,709 Hibbert et al Sept. 18, 1934 2,056,932 Day et a1. Oct. 6, 1936 2,172,661 Krauss Sept. 12, 1939 2,621,905 Daniell Dec. 16, 1952 FOREIGN PATENTS 361,642 Germany Oct. 17, 1922 494,204 Great Britain Oct. 21, 1938 

